Earthquake Alarm System Research Articles

B‐Positive: A Robust Estimator of Aftershock Magnitude Distribution in Transiently Incomplete Catalogs

AbstractThe earthquake magnitude‐frequency distribution is characterized by the b‐value, which describes the relative frequency of large versus small earthquakes. It has been suggested that changes in b‐value after an earthquake can be used to discriminate whether that earthquake is part of a foreshock sequence or a more typical mainshock‐aftershock sequence, with a decrease in b‐value heralding a larger earthquake to come. However, the measurement of b‐value during an active aftershock sequence is strongly biased by short‐term incompleteness of the earthquake catalog and by data‐windowing, and these biases have the same direction as the proposed signal. Here I develop a new estimator of the b‐value that is insensitive to transient changes in catalog completeness and that does not require data windowing. The new estimator “b‐positive” is based on the positive‐only subset of the differences in magnitude between successive earthquakes, which are described by a double‐exponential (Laplace) distribution with the same b‐value as the magnitude distribution itself. The b‐positive estimator greatly improves the robustness of continuous b‐value measurements during active earthquake sequences, as well as in historical catalogs with unknown or variable completeness. The new estimator confirms some of the observations of Gulia and Wiemer (2019), although at a reduced level, showing a decrease and recovery of the b‐value during several recent foreshock sequences that cannot be attributed simply to measurement bias. However, the unbiased b‐value changes may be too subtle to use in a real‐time earthquake alarm system.

A Study of Human Response in the Blind Zone of Earthquake Early Warning

The potential for seismic hazard in Taiwan is quite high. In addition to the comprehensive reinforcement of the earthquake resistance of old construction, a short period of time can be immediately is the implementation of earthquake prevention and rescue education. Because of the blind zone of the existing strong earthquake real-time alarm system, the response time is limited, so the application of the message will have better efficiency in an automated way. As regards the emergency response of schoolchildren and the population in the blind zone of strong earthquake early warning, it is suggested that people should be using methods in line with local circumstances. In order to understand and make good use of the vibration characteristics of seismic waves, this study analyzes and illustrates them with several practical examples, including (1) 20100304 Jiasian earthquake with local magnitude (ML) of 6.4,(2) 20130327 Nantou earthquake with local magnitude (ML) of 6.2, as well as (3) 19990921 Chi-Chi earthquake with moment magnitude (Mw) of 7.6. The results of this study show that the human body's feelings are one of the most direct, real-time strong earthquake warning messages, especially in the blind zone of earthquake early warning where it is too late to provide seismic information. Judging by the obvious vibrations up and down by the P wave, it is advisable for the people on the first floor of the old low earthquake-resistant premises to seize the opportunity and suggest a time take an immediate approach to outdoor escape response. While fear and panic may be an obstacle to escape, reflex movements can overcome fear, and reflex movements can be developed through regular drills. Accordingly, people will make a correct seismic response immediately within the earthquake, in a short period of time without panic of the emergency evacuation to reach a safe location.

Rapid Earthquake Alarm System and Real-Time Automated Action: Application of Multi-Agent Hardware

Rapid Earthquake Alarm System and Real-Time Automated Action: Application of Multi-Agent Hardware

Rapid Earthquake Alarm System and Real-Time Automated Action: Application of Multi-Agent Hardware

Earthquake is the most dangerous natural disaster in the whole era of human being life. Scientist efforts for predicting earthquake have no prolific result, so far. The earth complexity and geology structures are the main obstacles of these efforts. The importance of time at the occurrence of the earthquake has resulted in using powerful systems for real-time alarming and therefore lessening the casualties of the earthquake. In this paper we have designed a rapid earthquake alarm system and we have implemented it in parallel processing and continuous processing. We have tried to apply hardware intelligent agents for real-time and parallel processing of data and data fusion of sensors. By applying this technology, the performance of rapid earthquake alarm system will be improved. Through this improvement, the rapid and automated action of rapid earthquake alarm system can lead to reducing the effect of earthquake.

Earthquake Early Warning: ShakeAlert in the Pacific Northwest

We evaluate the performance of earthquake early warning algorithm ElarmS‐2 (earthquake alarm system v. 2) in the Pacific Northwest. Real‐time and prerecorded seismic data from Oregon, California, and Washington in the United States and British Columbia in Canada are used. The earthquakes tested range up to moment magnitude 7.2, the limit for which the ElarmS‐2 magnitude method is accurate. ElarmS‐2 reliably detects catalog magnitude 3 and larger earthquakes within the network, but the cut‐off magnitude for accurate event recognition is higher for events offshore and on the edges of the network. We have made several adjustments that make the ElarmS‐2 algorithm less likely to falsely report multiple alerts for earthquakes. Replaying of past earthquakes shows that the new settings improve the algorithm’s behavior for edge cases while not degrading previously well‐constrained solutions within the dense part of the network. We expect few false alerts, none that would predict significant shaking anywhere in our region. Even though ElarmS‐2 assumes a fixed earthquake depth, the epicenter and magnitude estimates are accurate enough to provide good predictions of shaking intensities. Online Material: Tables listing parameters of 31 calibration earthquakes, ElarmS‐2 real‐time detections, and comparison of ElarmS‐2 performance for calibration events before and after adjusting configuration.

Demonstration of the Cascadia G‐FAST Geodetic Earthquake Early Warning System for the Nisqually, Washington, Earthquake

ABSTRACT A prototype earthquake early warning (EEW) system is currently in development in the Pacific Northwest. We have taken a two‐stage approach to EEW: (1) detection and initial characterization using strong‐motion data with the Earthquake Alarm Systems (ElarmS) seismic early warning package and (2) the triggering of geodetic modeling modules using Global Navigation Satellite Systems data that help provide robust estimates of large‐magnitude earthquakes. In this article we demonstrate the performance of the latter, the Geodetic First Approximation of Size and Time (G‐FAST) geodetic early warning system, using simulated displacements for the 2001 M w 6.8 Nisqually earthquake. We test the timing and performance of the two G‐FAST source characterization modules, peak ground displacement scaling, and Centroid Moment Tensor‐driven finite‐fault‐slip modeling under ideal, latent, noisy, and incomplete data conditions. We show good agreement between source parameters computed by G‐FAST with previously published and postprocessed seismic and geodetic results for all test cases and modeling modules, and we discuss the challenges with integration into the U.S. Geological Survey’s ShakeAlert EEW system.

A global approach to provide magnitude estimates for earthquake early warning alerts

AbstractWe examine five different methods to estimate an earthquake's magnitude using only P wave data for use in earthquake early warning systems. We test two input parameters: the maximum predominant period of the P wave (τpmax) and the displacement amplitude of the P wave's vertical component (Pd). We apply our algorithms to 174 earthquakes 3.0 < M < 8.0 from California and Japan that have also been used in previous calibration studies. We also apply them to 1992 0.2 < M < 5.7 earthquakes that were processed by the real‐time Earthquake Alarm Systems in California. We find that τpmax does not scale with magnitude for small earthquakes (M < 3) and is less accurate for large‐magnitude earthquakes than using Pd alone. We derive a global scaling relation between Pd and magnitude and conclude that this global relationship provides the most accurate and robust magnitude estimate. This relationship could be applied in earthquake source zones around the world.

Designing a Network-Based Earthquake Early Warning Algorithm for California: ElarmS-2

The California Integrated Seismic Network (CISN) is developing an earthquake early warning (EEW) demonstration system for the state of California. Within this CISN ShakeAlert project, three algorithms are being tested, one of which is the network-based Earthquake Alarm Systems (ElarmS) EEW system. Over the last three years, the ElarmS algorithms have undergone a large-scale reassessment and have been recoded to solve technological and methodological challenges. The improved algorithms in the new production-grade version of the ElarmS version 2 (referred to as ElarmS-2 or E2) code maximize the current seismic network's configuration, hardware, and software per- formance capabilities, improving both the speed of the early warning processing and the accuracy of the warnings. E2 is designed as a modular code and consists of a new event monitor module with an improved associator that allows for more rapid association with fewer triggers, while also adding several new alert filter checks that help minimize false alarms. Here, we outline the methodology and summarize the performance of this new online real-time system. The online performance from 2 October 2012 to 15 February 2013 shows, on average, ElarmS currently issues an alert 8:68 � 3:73 sa fter the first P-wave detection for all events across California. This time is reduced by 2 s in regions with dense station instrumentation. Standard deviations of magnitude, origin time are 0.4 magnitude units, 1.2 s, and the median location errors is 3.8 km. E2 successfully detected 26 of 29 earthquakes (MANSS >3:5) across California, while issuing two false alarms. E2 is now delivering alerts to ShakeAlert, which in turn distributes warnings to test users.

Urgent Earthquake Detection and Alarm System that Supports the Safety of Japanese Railway

Urgent Earthquake Detection and Alarm System that Supports the Safety of Japanese Railway

The dynamics of a seismic wave field: Animation and analysis of kinematic GPS data recorded during the 2011 Tohoku-oki earthquake, Japan

[1] During rupture, earthquakes induce permanent and dynamic ground displacements that can be measured by GPS. More than 1200 continuous GPS stations distributed throughout Japan recorded the displacements due to the March 11, 2011, Mw9.0 Tohoku-oki earthquake. We animate these data, which shows the growth of the earthquake rupture over time and illustrates differences of earthquake magnitude through two smaller aftershocks. We also identify dynamic ground motion due to S-waves (body waves), Love waves and Rayleigh waves (surface waves) in this data set. Real time availability of such displacements could be of great use in earthquake response and tsunami warning, and to some degree in earthquake early warning. We find that the length of the ruptured fault can be approximated from displacements which could allow rapid identification of areas prone to large aftershocks. We outline a method that integrates real time displacements into an earthquake alarm system. The animated displacements in map view are easily understandable by specialists and non-specialists alike and hence provide a valuable education and outreach tool.

Development of the ElarmS methodology for earthquake early warning: Realtime application in California and offline testing in Japan

In July 2009, the California Integrated Seismic Network concluded a three-year study of earthquake early warning systems in California. Three algorithms were expanded and examined during the study. Here we discuss the history, methodology, and performance of one of the algorithms, ElarmS. Earthquake Alarm Systems, or ElarmS, uses peak displacement and maximum predominant frequency of the P-wave to detect earthquakes and quantify their hazard in the seconds after rupture begins. ElarmS was developed for Northern and Southern California, and now processes waveforms in realtime from 603 seismic sensors across the state. We outline the methodology as currently implemented, present several example events from different regions of California, and summarize the performance in terms of false and missed alarms. ElarmS was also tested offline with a dataset of 84 large magnitude earthquakes from Japan. The results from the Japan dataset were used to create a statistical error model for the algorithm. The model can be used to provide realtime uncertainty estimates at any stage in processing. In August 2009 the CISN embarked on a second three-year study of earthquake early warning. As part of this ongoing research, we identify the technological and methodological challenges facing ElarmS. Telemetry latencies and false alarm rates are two key opportunities for improvement.

Testing ElarmS in Japan

Earthquake early warning systems use seismic networks, rapid telemetry, and software algorithms to detect an earthquake immediately after its inception, estimate its damage potential, and disseminate a warning to surrounding communities before peak ground shaking occurs. Earthquake Alarm Systems, or ElarmS, is an earthquake early warning system developed in California. The ElarmS algorithm recognizes earthquakes from the initial P -wave arrivals at seismometers near the epicenter. The characteristics of the P wave, including amplitude and frequency, are used to estimate a final magnitude for the event. P -wave arrival times from several stations are combined to estimate the hypocenter of the event. Finally, the estimated magnitude and hypocenter are applied to attenuation relations to produce a prediction of ground shaking levels in the region. ElarmS has been tested extensively with datasets of earthquakes from northern and southern California (Allen and Kanamori 2003; Allen 2007; Wurman et al. 2007; Tsang et al. 2007; Allen et al. 2009). While the test datasets from California included a large range of locations and source types, there are a limited number of recent, well-recorded, large earthquakes available for testing the early warning system. In this study we take ElarmS to another geographic and seismic setting and test the algorithms with a dataset of 84 large-magnitude earthquakes, including 43 of magnitude 6.0 or greater, in Japan. The Japanese test dataset is valuable both for the insight into ElarmS' processing of large events and for the chance to process events in a completely different geologic setting. The offshore and deep nature of many of the events presents new challenges to the methodology. The Japanese earthquakes offer an opportunity to improve the robustness of ElarmS, extend its abilities to other settings, and confirm its relevance for large-magnitude events. The dataset contains 84 earthquakes recorded …

Toward earthquake early warning in northern California

Earthquake early warning systems are an approach to earthquake hazard mitigation which takes advantage of the rapid availability of earthquake information to quantify the hazard associated with an earthquake and issue a prediction of impending ground motion prior to its arrival in populated or otherwise sensitive areas. One such method, Earthquake Alarm Systems (ElarmS) has been under development in southern California and, more recently, in northern California. Event magnitude is estimated using the peak amplitude and the maximum predominant period of the initial P wave. ElarmS incorporates ground motion prediction equations and algorithms from ShakeMap for prediction of ground motions in advance of the S wave arrival. The first peak ground motion estimates are available 1 s after the first P wave trigger, and are updated each second thereafter for the duration of the event. The ElarmS methodology has been calibrated using 43 events ranging in size from ML 3.0 to Mw 7.1 that occurred in northern California since 2001. We present the results of this calibration, as well as the first implementation of ElarmS in an automated, noninteractive setting and the results of 8 months of noninteractive operation in northern California. Between February and September 2006, ElarmS successfully processed 75 events between Md 2.86 to Mw 5.0. We find that the ElarmS methodology processed these events reliably and accurately in the noninteractive setting. The median warning time afforded by this method is 49 s at the major population centers of the Bay Area. For these events the magnitude estimate is within an average of 0.5 units of the network‐derived magnitude, and the ground motion prediction from ElarmS is within an average of 0.1 units of the observed modified Mercalli intensity.

An Automatic Processing System for Broadcasting Earthquake Alarms

In Japan, most of the damage caused by large earthquakes is concentrated within areas less than about 100 km from the focal regions. We have developed an earthquake alarm system that determines earthquake parameters within a few seconds of the P wave’s arrival at the closest station, and then transmits the earthquake information before the S -wave arrival in areas of possible serious earthquake damage. Since an earthquake alarm system requires the determination of reliable earthquake parameters as quickly as possible, it is unreasonable to wait until waveform data from numerous stations have been collected for analysis. For this reason, we have developed a novel method of determining the hypocentral location by using the arrival times for only a few stations, as well as the lack of P -wave arrivals at other stations at a given time. The use of not-yet-arrived data makes it possible not only to determine reliable hypocenter parameters within a few seconds, but also to detect erroneous arrival-time readings and remove them automatically. Since the available waveform data increases with time, the system was designed to redetermine earthquake parameters every second. Our method was deployed in a real-time system starting in July 2002. The real-time system locates 10–20 events per day, which includes a few felt earthquakes occurring in and around Japan. It was shown from the waveform data for about 100 felt earthquakes that almost all the events, except those far from the network, could be located within a few seconds, when most of seismic energy has not even arrived at some stations close by. We recently started widespread broadcasting of earthquake information in real-time by using a satellite transmission system.

The potential for earthquake early warning in southern California.

Earthquake mitigation efforts in the United States currently use long-term probabilistic hazard assessments and rapid post-earthquake notification to reduce the potential damage of earthquakes. Here we present the seismological design for and demonstrate the feasibility of a short-term hazard warning system. Using data from past earthquakes, we show that our Earthquake Alarm System (ElarmS) could, with current TriNet instrumentation, issue a warning a few to tens of seconds ahead of damaging ground motion. The system uses the frequency content of the P-wave arrival to determine earthquake magnitude, an approach that allows magnitude determination before any damaging ground motion occurs.

An earthquake alarm system for the Maui A Offshore Platform, New Zealand

abstract An earthquake alarm system for the Maui A Offshore Platform, which is situated in the Tasman Sea off the coast of New Zealand for the production of natural gas, is described. The function of the alarm system is to give an immediate warning when accelerations equal to half the design level for the platform have been reached in order that safety procedures can be initiated. The alarm system was designed to monitor only the response of the lower modes of the platform, as these would make the major contribution to the stresses in the platform. Ambient vibration measurements were performed which showed the values of frequency for the six lowest modes to be in the range of 0.45 to 1.35 Hz. The alarm system was accordingly designed so that the signal from the transducers passed through a filter with a nominally flat frequency response over a bandwidth 0.3 to 2 Hz with a sharp roll-off at 24 dB per octave at higher frequencies. A radio link with similar detectors on shore was arranged to give confirmation that an earthquake had occurred in order to reduce the risk of false alarms.

An Earthquake Alarm System

This paper describes a four-channel Earthquake Alarm system designed to monitor four seismic stations located some distance apart. The sensitivity is set so that a Richter magnitude of 6.5 at 8,000 km appearing at three out of the four stations will trigger an alarm.

The use of the thyratron in an earthquake-alarm system*

The use of the thyratron in an earthquake-alarm system*